Evaluation of animal models through utilization of histological approaches leads to insights at the cellular and molecular levels. However, analysis of tissues in the musculoskeletal system is technically challenging due to the nature of the tissues involved, which requires specialized embedding approaches and anatomical knowledge to obtain the necessary sections, and the use of multiple staining techniques to visualize various matrix and cellular components. In 2009, we established the Musculoskeletal Histology and Morphometry Core to provide comprehensive technical and consultative services for our Research Community to optimize and take greatest advantage of their animal models for musculoskeletal biology and disease, including bone, cartilage, tendon, disc, and muscle. Since our inception, we have provided billable services for 88 unique investigators who have reported histological data in 192 manuscripts, which have been cited 3266 times (see Exhibit II.C and Bibiolography). In addition, we have presented seminars/workshops and developed online resources to promote appropriate qualitative and quantitative assessment of musculoskeletal histology and promote best practices, to support rigor and reproducibility. We have adapted to the needs of our Research Community by implementing non-decalcified frozen sections/tape transfer methods, commonly used with lineage tracing mouse models, and recently (in late 2017) acquiring a Leica confocal microscope system to aid in downstream analysis. We have also formed a collaborative interaction with Dr. James Fitzpatrick in the Washingotn University Center for Cellular Imaging (WUCCI) to take advantage of other cutting-edge microscopic techniques available on campus. We are currently implementing new techniques for histologic analysis of muscle, forming a new collaboration with Dr. Gretchen Meyer, a junior faculty member bringing this expertise into our Center. Going forward, we aim to sustain and extend these components of the Core with 5 objectives: 1) provide high quality, efficient histology services across the range of techniques required for musculoskeletal research; 2) support rigorous and reproducible approaches that contribute to research proposals and publications with high impact; 3) provide training and enrichment opportunities (in concert with the T32 Skeletal Disorders Training Program); 4) enhance and adapt Core services in response to the needs of our Research Community; 5) foster interactions among existing and new members of the Research Community through sharing of techniques and approaches for histology and microscopy. We have 2 Aims: Aim 1. Histology services: Perform processing, embedding, sectioning and staining, along with maintenance of protocols and targeted training for users, for the range of tissues and techniques required in musculoskeletal research. Aim 2. Resources for Histological Imaging and Analysis: Core will maintain and provide training for use of Leica Confocal microscope and BioQuant Osteo Histomorphometry software, as well as integration with the WUCCI which houses several light and electron microscopes.